for循环中未使用的变量

Question

def main():
    print ("This program illustrates a chaotic function")
    x = (float(input("Enter a number between 0 and 1: ")))
    for i in range(10):
        x = 3.9 * x * (1-x)
        print (x)

main()

When I type the program above into my Visual Studio Code desktop application, it returns the problem notification:

W0612: Unused variable 'i'

But when I run the same program with the built in python 'Idle' interpreter, the program runs just fine.

Answer 1

As you are not using ' i ' in for loop. Change it ' _ ' as shown in below

def main():
    print ("This program illustrates a chaotic function")
    x = (float(input("Enter a number between 0 and 1: ")))
    for _ in range(10):
        x = 3.9 * x * (1-x)
        print (x)

Answer 2

This is just your IDE alerting you that you have a variable defined, i , which you are not using.

Python doesn't care about this as the code runs fine, so the interpreter doesn't throw any error as there is no error!

There isn't really much more to say, Visual Studio is just notifying you in case you meant to use i at some point but forgot.

It is Python convention to use an underscore as the variable name when you are just using it as a placeholder, so I'd assume Visual Studio would recognise this and not notify you if you used _ instead of i .

Answer 3

This is about ignoring pylint warnings.

1st way:

adding #pylint: disable=unused-argument before for loop

2nd way: you can ignore them from pylint config file

[MESSAGES CONTROL]
disable=unused-argument

Answer 4

使用以下命令生成包含所有选项的 pylint rc 文件

pylint --generate-rcfile > $HOME/.pylintrc